Have you guys ever heard of super string/M-theory? Basicly it's based on these small little entities called gravitons. If a single atom was the size of the universe a single graviton would be to the scale size of a small tree. They're supposed to look like small viberating strings. Anyways, according to a handfull of physicists, this would reveal more demensions then the 4 we can "see" now... Up, down, side to side, and time.
Basicly the equations they work with reveal... More then one universe. In the sense of it being the same universe, only slightly diffrent (parellel). gravitons are the only "matter" that can move between the universes.
It's said that the number of universes, is infinite. And that we live in each. In one, one of us may be a great leader, in another, we might already be dead. Or perhaps everything is exactly the same, except this forum colour might be pink.
In one we might be dying, in another were starting to be born.
String theorists don't believe in 'death' or even 'birth'. But then again niether do a lot of normal/basic physicists. Also it's possible to disprove the big bang theory, as being the bang was one of many that were infinitely happening. No beginning and no end.
I don't understand the math behind the theory (you'd need a Phd in physics to understand). But the way they explain it, is so dilligent. Probably the most worked on theory to ever exist. Of course it may be wrong... I would like to think that it isn't though.